1. Environmental Science Inquiry and Applications Cunningham • Cunningham
Principles of
Environmental Science
Inquiry and Applications
Third Edition
Cunningham • Cunningham
Chapter 8 Lecture Outlines*
*See PowerPoint Image Slides for all figures and tables pre-inserted into PowerPoint without notes.
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2. Environmental Health and Toxicology
Chapter 8

3. Outline:
Environmental Health Hazards
Global Disease Burden
Emergent and Infectious Diseases
Antibiotics and Pesticide Resistance
Toxicology
Distribution and Fate of Toxins
Minimizing Toxic Effects
Measuring Toxicity
Risk Assessment
Public Policy

4. ENVIRONMENTAL HEALTH HAZARDS
Health - A state of complete physical, mental, and social well-being.
Disease - An abnormal change in the body’s condition that impairs important physical or psychological functions-.
Diet and nutrition, infectious agents, toxic chemicals, physical factors, and psychological stress all play roles in morbidity (illness) and mortality (death).

5. Figure 08.01

6. Global Disease Burden
Health agencies calculate disability-adjusted life years (DALYs) as a measure of disease burden.
Chronic diseases now account for nearly 60% of the 56.5 million total deaths worldwide each year.
Progress in eliminating communicable diseases such as smallpox, polio, and malaria, is allowing people to live longer.

7. Disability-Adjusted Life Year
WHO reports communicable diseases are responsible for nearly half of all 1.2 billion DALY’s lost each year.
About 90% of all DALY losses occur in developing world where one-tenth of all health care dollars are spent.
Malnutrition exacerbates many diseases.

8. Emergent Diseases and Infectious Diseases
An emergent disease is one not previously known or that has been absent for at least 20 years.
An important factor in the spread of many diseases is speed and frequency of modern travel.
Malaria is one of the most prevalent remaining infectious diseases.
SARS and Avian Flu
HIV/AIDS has the largest death toll from an emergent disease.

9. Figure 08.02

10. Figure 08.03

11. Ecological Diseases
Domestic animals and wildlife also experience sudden and widespread epidemics.
Distemper Virus (Seals)
Chronic Wasting Disease (Deer and Elk)
Transmissible Spongiform Encephalopathies
Black-Band Disease (Coral)

12. Figure 08.05

13. Figure 08.06

14. Infectious Disease Outbreaks

15. Antibiotic and Pesticide Resistance
Protozoan parasite that causes malaria is now resistant to most antibiotics, while the mosquitoes that transmit it have developed resistance to many insecticides.
Short life spans.
Speeds up natural selection and evolution.
Human tendency to overuse pesticides and antibiotics.

16. Antibiotic and Pesticide Resistance

17. Antibiotic Use
At least half of the 100 million antibiotic doses prescribed in the U.S every year are unnecessary or are the wrong drug.
Many people do not finish full-course.
More than half of all antibiotics manufactured in the U.S. are routinely fed to farm animals to stimulate weight gain.

18. Toxicology
Dangerous chemicals are divided into two broad categories:
Hazardous - Dangerous
Flammable, explosive, irritant, sensitizer, acid, caustic.
Toxic - Poisonous
Can be general or very specific. Often harmful even in dilute concentrations.

19. Toxicology Cont’d
Allergens - Substances that activate the immune system.
Antigens - Allergens that are recognized as foreign by white blood cells and stimulate the production of specific antibodies.
Other allergens act indirectly by binding to other materials so they become antigenic.

20. Toxicology Cont’d
Sick Building Syndrome
Headaches, allergies, and chronic fatigue caused by poorly ventilated indoor air contaminated by molds, carbon monoxide, nitrogen oxides, and other toxic chemicals.
Worker absenteeism and reduced productivity.
EPA estimates $60 billion annual loss.

21. Figure 08.08

22. Toxicology Cont’d
Neurotoxins - Special class of metabolic poisons that specifically attack nerve cells.
Different types act in different ways.
Heavy Metals kill nerve cells.
Anesthetics and Chlorinated Hydrocarbons disrupt nerve cell membranes.
Organophosphates and Carbamates inhibit signal transmission between nerve cells.

23. Toxicology Cont’d
Mutagens - Agents that damage or alter genetic material.
Radiation
Teratogens - Specifically cause abnormalities during embryonic growth and development.
Alcohol - Fetal Alcohol Syndrome
Carcinogens - Substances that cause cancer.
Cigarette smoke

24. Endocrine Hormone Disrupters
Chemicals that disrupt normal endocrine hormone functions.
Hormones are chemicals released in blood by glands to regulate development and function of tissues and organs elsewhere in the body.
Environmental Estrogens and Androgens

25. Figure 08.09

26. Diet
Strong correlation between cardiovascular disease and the amount of salt and fat in an individual’s diet.
Highly-processed foods, fat, and smoke-cured, high-nitrate meats appear to be associated with cancer.
Nearly 2/3 of all Americans are considered overweight.

27. DISTRIBUTION AND FATE OF TOXINS
Solubility - Chemicals are divided into two major groups:
Dissolve more readily in water.
Dissolve more readily in oil.
Water-soluble compounds move rapidly through the environment, and have ready access to most human cells.
Oil-soluble molecules generally need a carrier to move through the environment.

28. Figure 08.10

29. Bioaccumulation and Biomagnification
Cells have special mechanisms for Bioaccumulation - Selective absorption and storage.
Dilute toxins in the environment can build to dangerous levels inside cells and tissues.
Biomagnification - Toxic burden of a large number of organisms at a lower trophic level is accumulated and concentrated by a predator at a higher trophic level.

30. Persistence
Some chemical compounds are very unstable and degrade rapidly under most conditions, thus their concentrations decline quickly after release.
Others are more persistent.
Stability can cause problems because these materials persist in the environment and have unexpected effects far from their original use.
PBDE (flame-retardants in textiles)

31. Bioaccumulation

32. Chemical Interactions
Antagonistic Reaction - One material interferes with the effects, or stimulates the breakdown, of other chemicals.
Additive Reaction - Effects of each chemical are added to one another.
Synergistic Reaction - One substance multiplies the effect of the other.

33. MECHANISMS FOR MINIMIZING TOXIC EFFECTS
Every material can be poisonous under certain conditions.
Most chemicals have a safe threshold under which their effects are insignificant.
Metabolic Degradation
In mammals, the liver is the primary site of detoxification of both natural and introduced poisons.

34. Figure 08.11

35. Excretion
Effects of waste products and environmental toxins reduced by eliminating via excretion.
Breathing
Kidneys
Urine

36. MEASURING TOXICITY
Animal Testing
Most commonly used and widely accepted toxicity test is to expose a population of laboratory animals to measured doses of specific toxins.
Sensitivity differences pose a problem.
Dose Response Curves
LD50 - Dose at which 50% of the test population is sensitive.

37. Population Sensitivity Variations

38. Figure 08.15

39. LD50

40. Acute vs. Chronic Effects
Acute Effects - Caused by a single exposure and result in an immediate health problem.
Chronic Effects - Long-lasting. Can be result of single large dose or repeated smaller doses.
Very difficult to assess specific health effects due to other factors.

41. RISK ASSESSMENT
Factors influencing risk perception:
Rating risks based on agendas.
Most people have trouble with statistics.
Personal experiences can be misleading.
We have an exaggerated view of our abilities to control our fate.
News media sensationalizes rare events.
Irrational fears lead to overestimation of certain dangers.
Fear of the unknown.

42. Accepting Risks
Most people will tolerate a higher probability of occurrence of an event if the harm caused by that event is low.
Harm of greater severity is acceptable only at low levels of frequency.
EPA generally assumes 1 in 1 million is acceptable risk for environmental hazards.

44. ESTABLISHING PUBLIC POLICY
Biggest problem in making regulatory decisions is that we are usually exposed to many sources of harm, often unknowingly.
May not be reasonable to demand protection from every potentially harmful contaminant in our environment, no matter how small the risk.

45. Figure 08.p188

46. ESTABLISHING PUBLIC POLICY CONT’D
In setting standards for environmental toxins, need to consider:
Combined effects of different exposures.
Individual sensitivities within population.
Effects of chronic and acute exposures.

47. Summary:
Environmental Health Hazards
Infectious Organisms
Emergent Diseases
Antibiotics and Pesticide Resistance
Toxic Chemicals
Distribution and Fate of Toxins
Minimizing Toxic Effects
Measuring Toxicity
Risk Assessment
Public Policy